RRI T24E Chassis

[19Seventy7]

Just a quick thought,

I thought, if the tuner is dead, is it possible to "hard wire" an RF input in?

I did actually test it (Whether this was the best idea I don't know, but nothing major happened)

I disconnected the wire from the tuner in the main board, and put in a RF lead, with an attenuator before.

Turned the set on, no static, which was a change but no video nor audio.

I turned the attenuator up, and managed to get sound through. Still no picture, but no static.

Is it possible to somehow get a Freeview box, with RF out, and hardwire it into the main PCB, without going through the tuner.

Apologies about the picture, I completely forgot, and again don't have the space right now to get it out of storage and work on it again.

Thanks

[AlanC]

The quick answer is no. The tuner converts the incoming UHF aerial signal, in the range 470 to 860MHz down to a single, constant frequency called the intermediate frequency or IF for short. It does ths because the IF is much easier to filter, amplify and demodulate than the UHF signal.

The IF is usually around 38MHz, so the output of your freeview box, which is somewhere in the middle of the UHF band, is getting on for 20 times too high in frequency.

But this is not fixing your fault! You need to get a meter that gives sensible readings- Halfords sell one that's only about £13- and let's measure the voltages on the tuner. Though I think the problem is further down the chain from the symptoms you describe, that said I'm no expert compared to many of the guys on here!

Cheers
Alan

[toshiba tony]

Be very careful, your particular chassis I dont know but all Ranks offerings used a half live chassis. You can only go in via the aerial socket (isolated) You call it static, I presume you mean RF noise on the picture. I'll dig the manual out, and ask some further questions.

[19Seventy7]

Hi,

The quick answer is no. The tuner converts the incoming UHF aerial signal, in the range 470 to 860MHz down to a single, constant frequency

I actually thought that the tuner did the opposite, boosting the signal so it could be made into something the TV could display.

But this is not fixing your fault! You need to get a meter that gives sensible readings

No that's true, but I have been curious about "converting" a set to digital, and I thought it might be a good candidate with its poor tube, it wont be too much of a loss.

Is there a way the tuner can be fixed? I didn't think they could be. (Not that I have as much knowledge on TVs as others on here)

Be very careful, your particular chassis I dont know but all Ranks offerings used a half live chassis.

I did take precautions, not touching anything inside while the set was on, and making sure nothing was touching something it shouldn't be.

You call it static, I presume you mean RF noise on the picture.

I think so, I wasn't sure what it was called.

Thanks

[toshiba tony]

Yes but ANYTHING that is at a potential to earth should not be connected. This would free battery equipment but then you have the issue of connecting any item to the tv, well that would rend the item you are connecting to become live as well. I hope I'm not sounding boring about this. I have had 50 years in the trade, Sony and LG and mains is not kind to you. Are you getting anything on the screen, I think we can assume if you have sound, (any noise at all) the line output stage is working, try and post a few pictures of what you have on the screen.

[19Seventy7]

Okay, that makes sense, I thought it'd be okay as it's an input that it'd receive voltages, not give them out.

I'll definitely remember that.

I get a weird RF noise on screen, (see post #18) and I have fully working sound, and can get normal audio from a signal.

Thanks for your help

[jayceebee]

Originally Posted by 19Seventy7

...and I have fully working sound, and can get normal audio from a signal.

Sorry but are you saying you have normal program audio or just noise?

[19Seventy7]

Sorry, I get normal programme audio

Thanks

[toshiba tony]

If you have tunable audio what are using as an input source?

[19Seventy7]

Morning,

Im using a freeview box into a modulator, with RF out into the TV. (The modulator works, as I use it for other sets)

Thanks

[toshiba tony]

Hello, right, so you are coming out at composite and l\r into a modulator, yet you cant get a picture. Whatever you are seeing on the screen, noise or whatever, do the brightness and contrast have any effect? And you say the audio you can hear is from the freeview box?

[jayceebee]

Back in post 39 the OP says he had signs of chroma . It looks to me like some sort of decoder fault, there seems to be signs of the HF component of the video getting through to the CRT hence the noise noted but I can't help much as don't think I've ever seen inside a T24 or even a T22. I do remember repairing a handful of T20s with its singing chopper transformer.

[19Seventy7]

Hi,

Yes, the controls all take effect as they should and the audio comes from the freeview box.

As Jayceebee says, I have had signs of video getting to the CRT as i’ve had flashes of colours and outlines, but these only last for a split second.

Thanks for your help

[julie_m]

If you adjust the tuning on the TV back and forth, do you see a clear picture with no sound and then, a little further up the band, clear sound with a messed-up picture?

You say the modulator works with other TV sets -- are they all fairly modern ones?

[19Seventy7]

Hi,

No i dont get any picture, the sound always works, just no picture.

The modulator is used for other 1970s sets so I cant see that causing an issue.

I did wonder if the set could be VHF, but i dont know if this would affect sound.

Thanks

[jayceebee]

If you have programme sound then there's no problem with the tuner. If you could upload a video of the symptoms to YouTube it could help in diagnosing exactly what's going on.

John.

[G8vsjDave]

If you adjust the television tuning, does the sound come and go, or is the sound always there?
Dave

[19Seventy7]

The sound comes and goes, as it should.

I'll get to recording the video now to upload to YouTube

Thanks

[19Seventy7]

Hi,

I've uploaded the video, and there's information in the description.

(Will need an 18+ channel because of all the COPPA/FTC changes on YouTube)

https://www.youtube.com/watch?v=qh2BKauRHjA

Thanks

[jayceebee]

Ok, so I think we can safely say that there is no fault in the tuner or IF circuitry but without a diagram I'm not able to help much. As from previous posts this appears to be a Toshiba design and probably doesn't use the familiar TBA/TDA series of IC's in the decoder, may even possibly be a missing gating pulse from the line stage*. I've trawled through the back issues of TV mag here but I'm afraid I haven't been able to find anything on the T24.

EDIT. I've just re read through the whole thread and early on Welsh Anorak mentions a 36K resistor. Have you been able to locate it?